Key points:

UNICEF said: "We no longer have the words to describe children's suffering and our outrage"

In just a few days, about 210 people have been killed and about 850 injured, the Syrian Observatory for Human Rights said

"No words will do justice to the children killed, their mothers, their fathers and their loved ones," the release from UNICEF's regional director Geert Cappalaere began.

There followed 10 empty lines with quote marks indicating missing text, and an explanatory footnote.

"UNICEF is issuing this blank statement. We no longer have the words to describe children's suffering and our outrage," it said.

"Do those inflicting the suffering still have words to justify their barbaric acts?"

Eastern Ghouta is just east of the capital Damascus and is the last major opposition area near the city.

Forces loyal to President Bashar al-Assad have been besieging almost 400,000 civilians trapped inside Eastern Ghouta for years, but the siege has tightened this year and attacks on the enclave have intensified.

Opposition activists say government forces have brought in more reinforcements in recent days, while state media also said that the heavy bombardment "comes as the Syrian Army makes its final preparations for a massive ground offensive against armed rebel factions — to be the largest ever conducted within the vicinity of the Syrian capital — from multiple directions".

"The humanitarian situation of civilians in East Ghouta is spiralling out of control," said Panos Moumtzis, the UN regional humanitarian coordinator for the Syria crisis, in a statement.

"It's imperative to end this senseless human suffering now. Such targeting of innocent civilians and infrastructure must stop now."

UN Syria envoy Staffan de Mistura said in a press conference that East Ghouta was "becoming a second Aleppo", Syria's second city largely destroyed by years of fighting with thousands killed.

France said the attacks amounted to a serious violation of international humanitarian law, calling for a humanitarian truce.

The attacks "deliberately target inhabited areas and civilian infrastructure, including medical ones. They constitute a grave violation of international humanitarian law," the foreign ministry said in a statement.

"These acts engage the responsibility of the Syrian regime, but also that of Russia and Iran, which are its main backers and who, in the framework of the Astana agreements, have vouched for a ceasefire that is supposed to apply to Ghouta."

The confrontation pits the Turkish army and allied Syrian rebel groups directly against the military alliance backing the Assad Government, further scrambling north-west Syria's already messy battlefield.

Turkish state media reported that Turkish artillery had fired warning shots and forced the Syrian fighters back before they reached Afrin.

But Syrian television showed them passing through a checkpoint that bore the insignia of the Kurdish security force, some chanting "one Syria, one Syria", and driving further into the enclave.

Ankara's month-old offensive is aimed at driving the Kurdish YPG militia, which it sees as a big security threat on its border, from Afrin.

The YPG hailed the arrival of the pro-government forces — which included militias allied to Mr Assad but not the Syrian army itself — and said they were deploying along the front line facing the Turkish border.

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